Paleogene

The Paleogene is the geologic period from about 66 to 23 million years ago, following the Cretaceous and preceding the Neogene. It includes the Paleocene, Eocene, and Oligocene epochs.

Paleocene: The first epoch of the Paleogene, lasting from about 66 to 56 million years ago. It begins the period immediately after the end-Cretaceous mass extinction.
Paleocene–Eocene Thermal Maximum: A rapid global warming event about 56 million years ago, accompanied by major carbon release and ocean acidification. It sharply punctuated the Paleogene’s early climate history.
K–Pg extinction event: The mass extinction about 66 million years ago that eliminated non-avian dinosaurs and many other groups. Its aftermath set the ecological conditions at the Paleogene’s opening.
Adaptive radiation: The rapid diversification of a lineage into multiple forms adapted to different ecological roles. It describes how several mammal groups diversified after the K–Pg extinction.
Eocene: The epoch from about 56 to 34 million years ago, following the Paleocene and preceding the Oligocene. Its early warmth and later cooling mark the Paleogene’s middle epoch.
Eocene–Oligocene transition: A major climate shift about 34 million years ago, when global cooling and Antarctic glaciation intensified. It separates the warm Eocene from the cooler Oligocene.
PETM carbon isotope excursion: A large negative shift in carbon-isotope records marking rapid carbon release at the Paleocene–Eocene Thermal Maximum. It provides a measurable signal of a defining Paleogene warming event.
Primate: A mammal in the order Primates, which includes lemurs, monkeys, apes, and humans. Early primates appear in the Paleogene fossil record.
Oligocene: The final epoch of the Paleogene, lasting from about 34 to 23 million years ago. It closes the period as global climates cooled and Antarctic ice expanded.
Antarctic glaciation: The formation and expansion of continental ice sheets on Antarctica. Its onset in the late Eocene helped reshape Paleogene climate and oceans.

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